1. Field of the Invention
This invention relates to a cross dichroic prism and an optical system having the same, and is suitable, for example, as color separating means and/or color combining means for use in a color liquid crystal projector, a three-plate CCD camera or the like.
2. Related Background Art
A cross dichroic prism P as shown in FIGS. 13 and 14 of the accompanying drawings has heretofore been used as the color separating means or color combining means of a color liquid crystal projector.
The cross dichroic prism P, as shown in FIG. 13, comprises four rectangular prisms 1, 2, 3 and 4 of triangle poles cemented together so that the apex angles of those prisms may intersect with one another. A dichroic surface (film) is provided on the joined surface of each prism. The dichroic surface intersects with other surface at 90.degree..
The cross dichroic prism according to the prior art comprises four rectangular prisms cemented together as previously described and therefore suffers from the problem that it is bulky and heavy. Particularly in a liquid crystal projector using a liquid crystal panel provided with a microlens for condensing light for each pixel, a light beam emerging from the liquid crystal panel is great in angle of divergence due to the action of the microlens, and it has been necessary to make the cross dichroic prism provided between the liquid crystal panel and a projection lens considerably large.